1. Field of the Invention
The present invention pertains to a pressure plate assembly for a friction clutch, comprising a housing arrangement; a pressure plate held in the housing arrangement with freedom to move in the direction in which a rotational axis extends; a stored-energy element; a wear-compensating device acting in the path of force transmission between the stored-energy element and the pressure plate and/or the housing arrangement, which device has at least one adjusting element which can move in an adjusting direction to compensate for wear; and a clearance-producing arrangement, comprising at least one gripping element, which is attached to the assembly upon which the stored-energy element acts via the wear-compensating device. The minimum of one gripping element has a blocking section, by means of which it can make blocking contact with a blocking element when wear occurs, the clearance-producing arrangement also comprising an arresting element associated with the minimum of one gripping element. The arresting element can be displaced in the direction of the arresting motion upon the deflection, produced by the blocking system, of the minimum of one gripping element with respect to the assembly in question in order to arrest the gripping element in the deflected position associated with the amount of wear which has occurred.
2. Description of the Related Art
A pressure plate assembly with a design of this type is known from U.S. Pat. No. 6,123,180. Pressure plates of this type are usually manufactured by suppliers, who do not necessarily also produce the flywheels or clutch disks to be assembled with these pressure plates to arrive at a complete friction clutch. This means that these pressure plate assemblies are frequently delivered separately and are not attached to the clutch disks and flywheels to produce the complete friction clutches until they have arrived in the automotive assembly plant or some later production stage. This means that, in the stage before the pressure plate assembly is attached to the flywheel, there is initially no backing for the pressure plate. The stored-energy element, which is acting on the pressure plate, thus pushes the pressure plate outward from the housing arrangement; that is, there is no support such as that present after the flywheel and the clutch disk, which is situated between the pressure plate and the flywheel, have been attached. The flywheel and the clutch disk thus form a stop, which limits the movement of the pressure plate. A problem which exists in this type of production phase, i.e., the phase before the pressure plate has been attached to the flywheel, is that, as a result of the force exerted by the stored-energy element, the pressure plate can be pushed so far out of the housing arrangement that the gripping element (or the blocking section of the gripping element) enters into contact interaction with a blocking element, which can be attached, for example, to the housing arrangement. As a result, the subassemblies provided in the pressure plate assembly to respond to and to compensate for wear either go into operation or are brought into a state of readiness for such operation. This, however would ultimately mean that an unwanted wear-compensating operation would occur later, when the clutch disk is pushed back into the housing arrangement as it being attached to the flywheel and the clutch disk. The first result of this is that the friction clutch would be installed in the wrong position, and the second is that the installation position of the stored-energy element would be changed, leading to a corresponding change in its force characteristic.
The present invention has the object of improving the design of a pressure plate assembly of the general type in question so that, in the state before the pressure plate assembly is attached to additional components of a friction clutch, unwanted wear adjustments or measures preparatory to such adjustment do not occur.
In the pressure plate assembly according to the invention, a transport-securing arrangement is also provided, by means of which, before the pressure plate assembly is attached to the centrifugal mass arrangement, the minimum of one arresting element can be prevented from moving in the arresting direction and/or the minimum of one adjusting element can be prevented from moving in the adjusting direction.
By providing a transport-securing arrangement, which is effective especially in those areas of the pressure plate assembly which are critical with respect to unwanted wear adjustments, it is possible in a reliable manner to prevent the occurrence of a compensating movement when, in the transport condition, the pressure plate moves past its normal installation point in the friction clutch under the force of the stored-energy element and then is pushed back again into the housing arrangement during the assembly process. By providing a transport-securing device, it is possible, for example, to avoid the necessity of having to wait to install the blocking element provided to interact with the gripping element or the necessity of having to wait to bring the blocking element into its final installation position until after the friction clutch has been assembled. The means that some of the work steps involved in the process of assembling a friction clutch can be eliminated.
For example, a transport-securing section cooperating with the minimum of one adjusting element can be provided on the arresting element. This can be realized, for example, by providing the arresting element with an arresting interaction area, which, upon the occurrence of wear and the completion of a wear-compensating operation, allows limited relative movement between the minimum of one adjusting element and the arresting element, and by designing the transport-securing section on the arresting element in such a way that, in the transport state, it allows essentially no relative motion between the minimum of one adjusting element and the arresting element.
To allow the defined adjusting movement of the minimum of one adjusting element during the normal operating condition of a friction clutch but at the same time to be able to secure the assembly suitably for transport, it is proposed that, in the operating state of the clutch, the arresting interaction area engage in a recess in the adjusting element, which recess is elongated in the adjusting direction and is longer in the adjusting direction than the arresting interaction area, and that the arresting element have, in the area of the transport-securing section, a length in the adjusting direction which is essentially the same as the length of the recess. It can also be provided in the pressure plate assembly according to the invention that the arresting interaction area extends essentially in the radial direction into the recess and that the transport-securing section adjoins the arresting interaction area in the radial direction.
The transport-securing device will basically continue to perform its function during the process of attaching the pressure plate assembly to the flywheel or the like. To render this device inoperable so that the desired wear compensation function can be carried out during the normal operation of the clutch, it is proposed that the transport-securing device be brought out of its transport-securing interaction with the recess by the action of centrifugal force. This makes it possible to eliminate a separate set of work procedures for deactivating the transport-securing device.
Especially in an embodiment in which the transport-securing device acts essentially in the area of interaction between the arresting element and the minimum of one adjusting element, it is preferable to provide a release force-producing device, which acts on the pressure plate in the direction opposite that in which the stored-energy element exerts its force, the releasing force produced by the release force-producing device preventing the minimum of one adjusting element from moving by itself in the adjusting direction. Because the automatic movement of the adjusting element is prevented even after the wear-compensating device has ultimately been clamped between the stored-energy element and the release force-producing device by the actuating force exerted by the release force-producing device, ultimately the minimum of one adjusting element forms the component by which the arresting element is prevented from moving in the direction of its arresting movement. Only when vibrations or shaking motions occur while the vehicle is actually being driven will the minimum of one adjusting element assume a condition in which it is free to slide relative to the component against which it is supported, and it will then be able to move in the adjusting direction when a clutch-release operation is executed and the force being exerted by the stored-energy element is interrupted.
According to an alternative design of the present invention, a transport-securing section can be provided on the arresting element, which securing section can be brought into transport-securing interaction with an opposing transport-securing section provided in the area of the assembly in question and which, once the transport-securing interaction has been established, allows essentially no movement of the arresting element in the arresting direction. Here, therefore, a direct arresting interaction is produced between the arresting element and the assembly in question or a component provided thereon, so that ultimately, to prevent the movement of the arresting element in the arresting direction, it is no longer necessary to make use of the intermediate agency of the minimum of one adjusting element. This results in the advantage that, in the transport state, any impact-like movements which may occur, which could briefly shake the minimum of one adjusting element loose, cannot lead to the movement of the arresting element itself.
For example, the arresting element can be provided with an elongated body area stretching out in the direction of the arresting movement, which body area carries the transport securing section at one end. Here, too, it is advantageous for the transport-securing interaction between the transport-securing section and the opposing transport-securing section to be interrupted by the action of centrifugal force. This can be achieved, for example, by providing an essentially radially oriented transport-securing projection on one of the two sections, i.e., on the transport-securing section or on the opposing transport-securing section, and by providing an opening facing in the radial direction on the other one of the two sections. In an especially preferred embodiment, which ultimately requires no additional parts or components for producing the transport-securing interaction, the opposing transport-securing section can be provided on the gripping element. This can be achieved, for example, by providing the opposing transport-securing section at or near the end of the gripping element intended to produce the blocking interaction.
So that the transport-securing interaction can be obtained in the state in which the pressure plate is shifted axially relative to the housing arrangement without interfering with normal clutch or wear adjustment operations in the normal state, i.e., the state in which the pressure plate is pulled back into the housing arrangement, it is proposed that the arresting element be provided with an elongated body area, by means of which it is or can be brought into arresting interaction with the minimum of one gripping element under operating conditions; that the transport-securing section on the arresting element extend essentially along the body area but at a certain axial distance; and that it be possible for a free end of the transport-securing device to be brought into transport-securing interaction with the gripping element.
According to another design variant of the present invention, which is especially easy to manufacture, it is possible to provide a transport-securing section on the arresting element, which securing section can be brought into transport-securing interaction with an opposing transport-securing section on the stored-energy element. It is possible, for example, for the transport-securing section to comprise a transport-securing projection extending toward the stored-energy element and for the opposing transport-securing section to comprise an opening, facing in the axial direction, in the stored-energy element, preferably an opening between two of the spring tongues. Here, too, the transport-securing interaction can be easily deactivated again without any additional work if the transport-securing interaction between the transport-securing section and the opposing transport-securing section is produced in the first place by the axial displacement of the pressure plate relative to the housing arrangement under the action of the stored-energy element, the extent of this displacement exceeding the normal installation position of the pressure plate relative to the housing arrangement.
According to another alternative embodiment of the present invention, a transport-securing section can be provided on the minimum of one adjusting element, which securing section can be brought into transport-securing interaction with an opposing transport-securing section provided on the gripping element. For example, the opposing transport-securing section can be formed in the area of the blocking section of the gripping element.
In this embodiment, too, the transport-securing interaction can again be easily deactivated if the transport-securing interaction between the transport-securing section and the opposing transport-securing section is produced in the first place by the displacement of the pressure plate relative to the housing arrangement to an extent exceeding the normal installation position.
For example, it can be provided in this embodiment that the blocking section of the gripping element extends between the minimum of one adjusting element and the pressure plate, and that the transport-securing section is formed on the minimum of one adjusting element so that it extends toward the pressure plate.
Especially in the embodiment in which a transport-securing interaction is produced directly with respect to the minimum of one adjusting element, it is advantageous for the arresting element to have an arresting interaction area which engages in the opening provided in the minimum of one adjusting element with a certain play in the adjusting direction. By providing the arresting element with only a small amount of possible movement relative to the minimum of one adjusting element, it can be assured at the same time that the arresting element will not shift excessively along the minimum of one adjusting elements.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.